Horror that starts with a mother's panic instead of exposition. Ryoka wakes to increasingly desperate texts, no context, forced to piece together why the world is ending from a parent too terrified to explain it straight. The thing on the roof doesn't matter as much as the fact that her mom knows something catastrophic and can only warn her daughter in fragments. That asymmetry of knowledge, that helplessness of being kept in the dark by the person who's supposed to protect you, becomes scarier than whatever's actually waiting outside.

Ryoka wakes to her phone buzzing with frantic messages from her mother. Something is badly wrong, but Mom will not say what, insisting nothing could properly describe it. On Christmas Eve, high school student Ryouka Tsurumi learns that her building has been evacuated and the area sealed off because of a dangerous unknown creature called X, which may be sitting on the roof. X can hypnotize people and hunts humans for their blood so it can reproduce. The only other person left inside is her childhood friend Shuuhei Murosaka, and their first attempt to escape ends in disaster. When Ryouka wakes in her room again to face a different X, she realizes she is caught in a time loop. She teams up with Shuuhei to find a future where they survive. Over six short episodes, the story blends horror and mystery.